Gravel Issue #022

The suspension bible for gravel and road bikes – Understanding drop bar suspension elements

09.03.2023
by Mike Hunger, Robin Schmitt, Benjamin Topf


Drop bar bikes with suspension elements are taking the market by storm. What suspension concepts are there and what purpose do they serve? Why should drop bar suspension elements necessarily differ from MTB suspension? What does actually matter when it comes to suspension and aren’t there better ways to achieve the same results?

Content

If you’re up to date with the latest developments in the drop bar segment, you must have realised that increasingly more bikes come equipped with suspension elements. But is it just a transient trend or is drop bar suspension here to stay?

Many modern drop bar bikes feature self-damping components. Amongst the most popular ones are cleverly designed frames, futuristic cockpits and tires in all imaginable configurations, which are paired with either stiff or compliant wheelsets such as the Zipp 101 XPLR. However, even parts that at first glance might seem irrelevant to the performance of a bike, like a banal handlebar tape, can improve comfort and influence the bike’s handling characteristics. Alongside compliant frames and components, there’s currently a huge range of suspension elements available on the market. For example, many new gravel bikes come equipped with suspension forks like the RockShox Rudy or similar suspension concepts like BMC’s HiRide system, which sits inside the lower head tube between the fork crown and frame. Other manufacturers replace a conventional suspension fork with a sprung cockpit, like Specialized’s Future Shock. Some suspension systems can be retrofitted, like the Redshift ShockStop system, which consists of a suspended stem and seatpost. Alongside suspension dropper posts, there are several different rear suspension systems, like Trek IsoSpeed, BMC Micro Travel and Wilier ActiFlex 2.0. The Specialized Future Shock Rear of the new Diverge STR, on the other hand, is a completely new interpretation of the classic rear suspension concept. However, whether it’s better or not is a completely different question – one we’re going to answer in this article too!

In good-old GRAN FONDO fashion, as true drop bar fans we welcome every opportunity that comes our way and use it as a chance to give you a thorough overview of the market, providing you with some exciting new insights, lots of surprises and several effective suspension alternatives to improve comfort and control, some of which we already own and are totally free!

Is history repeating itself? The origins of road and gravel bike suspension.

A few decades ago “suspended or rigid” wasn’t even a question. Just like many modern gravel bikes, the first mountain bikes were unsprung, both at the front and rear. And if you think that drop bar suspension is a new thing, you’re mistaken! In 1992 and 1993 Gilbert Duclos-Lasalle won the legendary Paris-Roubaix spring classic with a RockShox suspension fork based on the MAG21. In 1995, RockShox introduced the Paris-Roubaix suspension fork, specifically aimed at the cobbles of the popular spring classic. At 30 mm, it generated just as much travel as one of today’s RockShox Rudy variants.

Generation Y – (why) do we even need spring elements?

Before delving deeper into all the different suspension concepts, we should clarify what the aim of a spring element is on a drop bar bike. The “smoother is faster” mantra has been lurking in the bike world for a while. Especially when riding gravel bikes, we love to explore the unknown and ride mostly off-road. This is where suspension elements can make a huge difference on a drop bar bike, ensuring more composed handling on rough terrain. Not only does this improve riding fun but also inspires more confidence, preventing the bike from bucking you off the saddle with bigger impacts. If you like to embark on epic adventures with your bike, suspension elements encourage you to drop into easy trails, because they provide additional reserves. As a result, gravel bikes could be a cool option for mountain bikers too! Remember, every bump costs propulsion and traction, thus putting more strain on both the rider and materials and inevitably leading to fatigue at an earlier stage. Suspension elements help to maintain your performance over a longer period of time, making long rides less strenuous. However, with the advantages often come disadvantages, because suspension elements have a detrimental effect on both the efficiency and weight of a bike while at the same time adding complexity to the whole system. With traditional road and gravel bikes with rigid frames, the geometry remains unchanged at all times and in every riding situation. When you use an active suspension element, on the other hand, it’s a whole other story. A suspension fork, for example, changes the head angle and wheelbase length, which isn’t ideal, especially if you spend lots of time on tarmac.


Pros

  • More comfort and less fatigue = higher performance
  • Enables more potent bikes
  • More riding fun


Cons

  • Additional weight
  • Not always pleasing aesthetically
  • Requires more maintenance
  • Alters the geometry

Why should drop bar suspension elements necessarily be different from MTB suspension systems?

Why not just put MTB suspension onto a gravel frame? Unfortunately, it’s not that simple, because the weighting of the individual parameters is completely different.

  • The size of the impact and the suspension’s capacity to absorb it.
  • Acceptable weight increase
  • Efficiency
  • Maintenance effort and complexity
  • Adjustability
  • Design
  • Geometry alterations as the suspension compresses
  • The geometry of road and gravel bikes would render a conventional mtb fork inefficient.

Unlike mountain bikes, gravel bikes are designed to ride both on and off road and to deal with far smaller impacts. Accordingly, both the size of the impacts and the bike’s ability to absorb them is significantly lower. As a result, the suspension elements of road and gravel bikes don’t take as much abuse and don’t have to be designed for maximum robustness. That being said, a gravel bike with suspension still weighs significantly more compared to one with a fully rigid frame. Moreover, suspension elements increase not only the weight of a bike but also the complexity, with suspension forks in particular being more prone to breakdown and requiring more maintenance.

Over the past two decades, the evolution of mountain bike rear suspension systems has revolved around one pivotal question: how do you create a suspension design that doesn’t drain the rider? Bikes have to be as efficient as possible to convert the power generated by our legs into propulsion. Needless to say, ebikes are a completely different story because they have the additional power of the motor. Riding a bike is a highly dynamic action. Unlike motorcycles, which have a permanent motor with smooth power delivery and relatively static riding position, bicycles keep you moving all the time, with big shifts in weight distribution with each pedal stroke. Pedalling efficiency describes the bike’s ability to transfer the energy generated by your legs to the rear wheel when pedalling. While doing so, it’s crucial that the suspension doesn’t fritter away energy. Especially when sprinting, a stiff frame ensures better efficiency.

On gravel bikes with rigid frames, the geometry remains unaltered in all riding situations. However, this changes as soon as you add a spring element. With flexing seatposts and decoupled seat tubes, the seat angle changes to varying degrees depending on saddle extension. When a suspension fork compresses, the front of the bike dives, altering the riding position and causing the wheelbase to shorten while at the same time steepening up both the head and seat angle.

Why not ride a mountain bike in the first place?

Hardly any other component epitomises the division between mountain bikes and drop bar bikes as well as drop bars themselves. These allow for several grip positions, allowing you to swap between several riding positions. Drop Bar bikes are usually stiffer and more precise than mountain bikes, which, among other things, is due primarily to the narrower tires and frame construction. In our Gravel vs. mountain bike article you’ll find an exciting comparison between the two concepts!

What gravel-specific suspension elements are there, and how do they work?

Now that we’ve clarified why drop bar suspension and mountain bike suspension aren’t interchangeable, we can take a closer look at all the different suspension concepts.

Two-part seatposts, like Canyon’s S25 VCLS 2.0 CF

The German direct-sales brand relies on carbon leaf spring technology: their patented design generates up to 20 mm travel and is claimed to be 100% maintenance-free. However, the degree of stiffness can’t be tuned and changes noticeably with increasing saddle height and rider weight. In addition, the seatpost movement isn’t damped and tends to bounce with impacts. With MTB full-suspension bikes, we talk about wheel path, which is the exact line that the axle of the rear wheel follows during a full compression of the suspension. With bikes that rely on a flexing seatpost instead of conventional suspension components, the post flexes in a sloping curve that changes the saddle angle over the travel, making you feel as if you were slipping backwards off the saddle. However, Canyon rely on a two-part design that ensures a very low degree of saddle tilt.

Trek IsoSpeed

With their IsoSpeed system, Trek decouple the seat tube from the top tube to allow more vertical flex. Moreover, the American brand replaces a conventional internal seatpost with an external mast, which sits over the top of the seat tube, allowing it to flex more. The mast is available in two lengths, which coupled with saddle height and rider weight can significantly influence the amount of deflection. While the previous version still allowed you to adjust the system to the rider’s weight and riding style to a certain degree, the current IsoSpeed system forgoes any kind of adjustments to reduce weight. This system allows for a stiff, efficient frame when riding out of the saddle while reducing vibrations while seated.

Rear suspension systems like Specialized’s Rear Future Shock

With the new Specialized Diverge STR, the Californian brand employs the newly developed, proprietary rear Future Shock, which completely reinterprets the full-suspension concept and transposes it into the gravel sector. The system generates around 30 mm of travel and uses the seat tube as a spring, attached to a damper in the top tube. An interchangeable frame post allows you to change the spring rate to suit your riding style, weight and height. Simply put, the frame post is the spring of the Diverge’s suspension system. This is available in 9 variants with different degrees of stiffness, each of which can be installed in two different orientations, providing different degrees of stiffness, and in turn different spring rates. The damper in the top tube regulates both the compression stage and rebound, thus controlling the speed that the seatpost can flex back away from the frame and the return. The damper can be adjusted on the fly using a 3-stage compression lever, while the rebound speed can be changed with an Allen key on the underside of the top tube. When sprinting out of the saddle, the frame of the Diverge STR remains stiff, while the sprung rear end of full suspension bikes tend to wallow, influencing the bike’s riding performance. In some riding situations, the rear end bobs excessively unless you reach for the two-stage compression damping adjustment to stiffen it up. One disadvantage: The damper cannot be serviced and is a wear item according to Specialized. However, the damper only needs replacing if it has a problem and is supposed to last longer than the 2-year warranty period.

Suspension dropper posts like the SRAM Reverb AXS XPLR

Depending on the model variant, the SRAM Reverb AXS XPLR dropper post offers 50–75 mm travel. However, with a 27.2 mm seat post diameter, it isn’t compatible with many drop bar bike frames. When dropping the post slightly, for example when riding off road, the SRAM Reverb AXS XPLR automatically switches to ActiveRide mode, which offers extra compliance and acts as an active suspension element. However, the system is meant to provide comfort while riding seated rather than improving rear-wheel traction. Moreover, the lower saddle inspires confidence downhill and improves comfort when riding seated. The SRAM Reverb AXS XPLR dropper post isn’t compatible with many drop bar bikes, because it’s only available with a 27.2 mm diameter. For gravel bikes with larger seat tubes, like for example the YT SZEPTER which has a 30.9 mm seat tube, you can run a conventional MTB dropper post instead, with significantly more travel.

Elastomer systems such as the Wilier Granturismo SLR and BMC URS

In this case, the rear end of the bike employs an elastomer that can both stretch and compress. Thanks to its elasticity, it can absorb impacts to a large degree and mitigate their effect on the rider. The downside is that some of these concepts (e.g. BMC) cannot be adapted to the rider’s needs. The Wilier uses different 3D printed elastomer inserts, allowing you to adjust the system to suit different rider weights. That being said, fine tuning the system isn’t an option.

Future Shock 2.0 suspension cockpit

Here the suspension element sits between the stem and head tube, allowing the cockpit to move vertically in relation to the head tube and frame. Simply put, the Future Shock system suspends the entire cockpit without affecting handling. A conventional MTB suspension fork, on the other hand, changes the head angle significantly when compressed. By rotating the headset cap you can adjust the damping setting and even lock out the system entirely.

Suspension stems like the Redshift ShockStop

The Redshift ShockStop system currently consists of two components: the stem and seatpost. Inside the stem, you’ll find two elastomers that control the suspension. To set up the system you’ll have to remove the handlebars to access the internals. The stem comes standard with five different elastomers with different firmness, which are graded in 10 kg intervals. A soft setup ensures plenty of comfort when riding seated but causes the handlebars to dive and flutter with abrupt braking manoeuvres and when sprinting out of the saddle. With a stiffer configuration, on the other hand, the system reacts mainly to bigger hits, but as a result keeps the bars in a more consistent position while still absorbing smaller vibrations to an extent. Compared to the Future Shock 2.0 system, the handlebars move in a radius around the pivot rather than translating up and down.

Suspension seatposts like the Redshift ShockStop

Different to the stem, the suspension of the Redshift ShockStop seatpost is controlled by a sprung parallelogram design. A threaded adjuster at the base of the seatpost lets you adapt the spring preload to suit your weight. The system gobbles up all sorts of bumps, from small chatter to nasty potholes. The spring is driven by a greased piston, which helps provide a small amount of damping, preventing the post from compressing or rebounding too quickly.

BMC HiRide System

The BMC HiRide system sits right between the fork and head tube and consists of a steel spring and hydraulic damper. Three different spring stiffnesses and three different preload spacers are available for the HiRide system. Using the spacer, you can set the recommended SAG of 5 mm, which leaves approximately 12 mm travel minus the upper and lower end stops. However, this procedure requires a special tool, which means that you’ll have to get it done by your local BMC dealer and on the fly setup changes aren’t an option. Compared to a conventional suspension fork, the HiRide system responds less sensitively, which is mainly due to the combination of a steel spring and hydraulic damper. Like with the Future Shock system, you can adjust the damping setting and even lock out the suspension entirely by rotating the stem cap.

Conventional suspension fork

While conventional suspension forks may seem more rudimental than some new, innovative suspension concepts, most riders are familiar with them. Whether it’s the RockShox Rudy Ultimate or Cannondale’s Lefty, they all generate between 30 and 40 mm of travel and can be easily adjusted to suit your needs and requirements simply by adding or removing air from a valve. However, it’s worth noting that due to the small amount of travel, they only allow for a minimal adjustment range, meaning that changes are hardly noticeable. Moreover, a suspension fork weighs around 700–900 g more than a rigid fork and also alters the geometry of the bike when compressed. On top of that, suspension forks don’t feature mounting points for bags, which could be a major setback for bike packers. Let’s be honest, most gravel forks look like cheap trekking forks. An elegant upside-down XC fork like the RockShox RS1 matches the look of a gravel bike a lot better – but also costs a lot more. Incidentally, this is also one of the reasons why you hardly ever see a FOX 32 TC suspension fork: because it’s too expensive!

Fatter tires or a suspension fork?

With all bikes, the tires are the only point of contact with the ground, which makes them a crucial component. Tires are a cheap and effective upgrade and will improve comfort, traction and control – provided the fork and frame offer enough clearance. The overall performance of a tire depends on many factors including tread pattern, tire casing and rubber compound. Although bigger and thus more voluminous tires can change the ride feeling entirely, they generally call for compromises: for example, when running low air pressures, the tire cushions impacts more efficiently but also makes for vague handling and higher rolling resistance on tarmac. It’s therefore important to find a good compromise. More often than not, finding the right air pressure makes all the difference, because it allows you to find the perfect compromise between damping, rolling resistance and grip on loose terrain. Using the right rim is just as important. If you mount a voluminous tire on a narrow rim, the tire can fold in corners. As a rule of thumb, the tire should form a U shape on the rim rather than a balloon-shaped O when inflated. That way the tire offers more lateral support and consequently also handles better through corners. There are two more factors to take into account: the maximum tire clearance of the frame and fork and the fact that a tire could be slightly wider than specified by the manufacturer when paired with a rim with a wider inner width.

Suspension without damping ≠ control

In a nutshell, suspension isn’t everything, because suspension without damping = little control – just try to picture a bouncy ball! That’s exactly what happens when there’s too much pressure in your tires.
In a conventional suspension fork or shock, the spring ensures that the wheel can compress or rebound, while the damping controls the speed of this movement during compression (compression damping) and during extension (rebound damping) by means of a valve that regulates oil flow. Systems without damping lack this control, meaning that the suspension travel is used up much too quickly or bounces harshly. For example, the Future Shock of the Specialized Roubaix Expert 2017 provides additional comfort on rough asphalt but quickly reaches its limits with a sporty and dynamic riding style. Needless to say, this comes at the expense of control and safety. Generally speaking, the best suspension system is only as good as the way it is adjusted to the weight, height and style of the rider.

Aren’t there better ways to achieve the same results?

If you want to run a simple set-up, save weight or simply avoid having too much complex technology on your bike, there are plenty of alternatives out there. For example, a sensible tire/wheel combination with the right air pressure, a different saddle and the right choice of frame material and components will already make a huge difference in terms of comfort. Upgrading to a dropper post will provide significantly more freedom of movement on descents and rough trails, while wider handlebars with more flare or flat bars will improve control and safety – even using a different bar tape could bring some advantages. Needless to say, both the frame geometry and size of the brake rotors have a huge influence on the off road capabilities of a bike and your perception of safety. Alternatively, you could invest your money in a riding skill course if you tend to ride primarily on trails – but then you might be better off buying a MTB ;).

Working on yourself: More skills, not more technology.

Remember, you’re the heaviest component of the entire bike-rider system! Oddly enough, you’re also the one that generates the most suspension travel. After all, both your arms and legs have the capacity to absorb impacts, even big ones, and are therefore a spring and damping system in their own right. However, this is only possible if you have the right set of skills, a dialled riding technique and enough freedom of movement on the bike. Handlebar ergonomics play a decisive role in this respect: If you ride in the drops of racing handlebars, your elbows are heavily bent, which means that your arms can only function as a “suspension fork” to a limited extent. Flared handlebars ensure more freedom of movement for your arms and provide more control than classic drop bars.

If you look at cyclocrossers, you’ll notice that they keep their hands predominantly on the hoods, because this position ensures excellent control and at the same time allows you to generate more suspension travel with your arms. Wide MTB handlebars are even more effective here, because they put you in a push-up-like position in which you can use your entire upper body (chest, shoulders and arms) to absorb impacts and generate plenty of “travel”. And it’s a similar story with the legs, because if you’re strong enough to climb to the top of the Passo Stelvio or finish the Unbound Gravel Race in one piece, you should have enough power in your legs to absorb hard blows from roots and rocks when the gravel path turns rough. But here’s the problem: with many bikes, the high saddle doesn’t give you enough freedom of movement to use your legs as a natural suspension element.

Our arms and legs provide most of the suspension travel and allow us to absorb even big, nasty hits – provided you know what you’re doing!

So for what applications does it make sense to use suspension elements? And what’s the right suspension concept for me?

Whether you’re a beginner or experienced rider, a commuter, adventurer or a racer, suspension elements can bring some real benefits. It all depends on your personal preferences and requirements: what type of terrain do you ride, and how do you ride it? How much complexity and (additional) cost are you ready to embrace? Are you after timeless functionality or exciting innovations and the latest technologies? The fact is: you don’t necessarily need suspension on a gravel bike, because other components, for example dropper posts, sometimes offer even more off-road performance.


Do you just want to cruise along and want to improve comfort?

In that case, weight and direct handling only play a subordinate role – effective damping and shock absorption are key on long rides.


Do you want to win races?

Race ≠ Race. Especially when racing short distances, less is often more. The longer and more intense the race, the more important it’s to minimise physical fatigue. Lightweight, efficient suspension elements help you ride for longer! Oh yes, at the end of the day, winning races is also down to tactics and fitness 😉


Are you looking to improve your off-road power and safety?

Then maximum freedom of movement and traction are paramount. This will inspire more confidence and make you feel safer and faster, while at the same time boosting the fun factor in demanding terrain. A dropper post is almost a must here, because it inspires more confidence than a suspension fork! Tires that generate plenty of traction and a matching wheelset are essential too!


The latest shit or reliable, proven material? How much technology do you want on your bike?

We love gravel bikes because they’re simple. Do you really want to add complexity to a simple product like a gravel bike? Wireless shifting, suspension elements front and rear, countless moving parts – the days of simple, maintenance-free gravel bikes are over. Overall, drop bar bikes are becoming increasingly more complex, which might be fascinating and fun, but also requires more thought, maintenance and planning. Are all the batteries charged? Are the moving parts and suspension elements clean and greased (if applicable)? Long-term tests have shown that suspension elements need regular servicing, while moving parts can quickly get dirty and start creaking!

Just as important as the suspension element is the bike itself and its interaction with other components. Because there’s a variety of different components for drop bar bikes available on the market. If you want to do things properly, you should remember a few things. For example, if you want to upgrade to a suspension fork, you should know that this has a different axle-crown length, which alters the geometry of the bike. The good-old “more is more” saying doesn’t necessarily apply here either: if you combine soft suspension with a soft saddle, for instance, you’ll get spongy handling. As is so often the case, finding the right compromise is key!

Conclusion


Suspension elements on gravel bikes are an exciting and logical development. That being said, not everyone needs or should use suspension. There are also other ways to achieve the same goal. Our body alone provides most of the travel, and with a dropper post or a few skill classes we’ll often achieve more, especially when it comes to off-road performance. In order to find the right suspension concept for you, you should think in advance. The fact is: suspension on gravel isn’t necessarily useful for everyone.

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Words: Mike Hunger, Robin Schmitt, Benjamin Topf Photos: Peter Walker, Benjamin Topf, Etienne Schoeman, Robin Schmitt, Andreas Maschke

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